Trestle ladder lock



Sept. 15, 1936. c. A. BARRETT TRESTLE LADDER LOCK Filed Au 50, 1935 s Sheets-Sheet 2 nt a wdmw film a v w n5 z 1 M Sept. 15, 1936. c. A. BARRETT TRESTLE LADDER LOCK s Sheets-SheetG Filed Aug. 50, 1935 Inventor; U/zarZeJA.fiar/etz;

fl w/2M1 X 7%W? Alta/W5C Patented Sept. 15, 1936 UNITED STAT ES PATENT OFF- I 'CYE TRESTLE LADDER LOCK Charles. A; Barrett, Brighton, Mass.-

Application August.30, 1935, Serial No., 38,543;

6 Claims.

This invention relates to improvements in trestle ladders, and particularly to trestle ladders of the extension type in which the ladder in!- cludes two trestle ladder members hinged tod gether at their upper ends and adapted to receive a vertically slidable extensionladder therebetween.

Extension trestle ladders have been in use in-v whichthe-trestle ladder members arehinged to- 105 gether at their upper ends, are connected by spreader hinge members betweentheupper and lower ends and are adapted to' receive and; guide a vertically adjustable extensionladder member. The trestle ladder members have beenf'ormedat 5 their upper ends to wedge against the-side bars of: the extensionladden to prevent wabb1ing,=and any load. placed upon the extension ladder. increasesthe wedging engagement. The extension ladder has. been. locked in position by apair of. swingable arms at the top of thetrestleimembers, which extend beneath a-.rung on: the ex!-. tension ladder. to prevent downward. movement; This; form: of trestle: ladder; has been very; difficult toproperly adjust since thepextensionladeder. member cannot? bev pushed up;and automatie cally-locked'in position from the ground,;and if the workmaneclimbsthe trestle ladder to pull up the extension ladder, the added weight on the trestle zladder causes-a. gripping engagement with 3- the extension .ladderand makes it-difiicult to move the extension ladder.- Extension ladders not of the-trestle type have beenin' usewith automatic locks whereby the extension ladder part: can: be pushed upwardsand be automaticallylocked at 3 the desired. position. These ladders, have been relatively: easy to-release forlowering of the, extension ladder.

It is :an; object of the present invention to. provide an extension trestle ladder in- WhiChi the 40' extension part canbe-readily adjusted and auto.-

matically lockeddnposition from the-ground;

It is further an object of they presentinvention to: provide an, automatic lock for. the extension part of a trestleladder. which. will also serve as 45 means: forwedgingthe extension ladder part to p revent-;wabbling ofthe ladder, such asmay-occur ini. wearof, the ladder'parts.

. Specifically; it is, an objectof the present inventionto .mount: a ladderlock housing on a trestle 5.9 partner jthe, ladder, whichincludes, thereinaslide able lockingv member adapted,- to engage. a. rung of: the extensionladder, the lockingmember-being. connected to. a. wedge. member'which; is pulled down whenthe. ladder is locked, in place and; wedges between the upper end:of: the trestle part and aside rail of the extension, ladder.

Further obj e.cts;, and; advantages of the .present. improvements-will be more readily apparent from the, following description; of. a. preferred embodie mentor, the;invention taken-'1 inconnection, with the. attached L. drawings, in which:

Fig; 1 is a side elevation of the trestle ladder;

Fig. 2 is a front elevation: of: thertrestl'e'ladder shown; in: perspective.

Fig. 3 is;a verticalsectiontaken on the plane indicated. 33, in- Fig; 2,: and in which: the, 110115? ing; of the lockis partially broken away;.

Fig. 4 is: a view of. the ladder-lock. takenpon: the; plane indicated. 4-4 in- Fig. 3.

Fig; 5-.is; avview. similar: to Fig; 3but showing;a different position of the parts-.offithe ladder lock.

Fig. 6 is a detailhorizontal:section-taken onthe plane-indicated66 in Fig, l-showing the spreader hinge members andguide; and

Fig. 7.is a detail front elevation of: the portion shown in Fig, 6.

Figs. land-2 illustrate'the assembly ofthetrestle ladder; Theladder includes'the trestle ladder members Illl0and:theextensionladder I2. Each ofthe, trestle members; I D-l 0, include; the side bars l4.-i4.- connected by the-runs IS. The side bars-spread downwardly from: the top. towards the bottom ofv the ladders.v The-trestle ladder members I 0-'l 0 are connected. at their upper ends by. the hinge members l'|-l'|, and the spread between the trestle members Ill-I0 is-limited by' a. pair ofhingemembers |8'-20 which arepivotally connected to themembers Hi-lllat 22 and 24 respectively andrarepivotally connected together. at' 26. The hinge partl8-has 40 aslot 28 adapted to receive the bent tongue 3ll on theihinge part 20 to .lockthehinge parts-when they. reach alignment as clearly illustrated in Fi 6.

The extension ladder. includes side bars 32 connected. by the rungs. 34. Thespreader hinge members Iii-20 carry guide parts.36 which receive and guide the-side: bars.32-. of. the extension ladden. One'of! the-sidebars Itof each of the trestleladder members I0:is formedat itsupper 5.0

end with a beveled surface 38 to bear against a side bar 32 of the extension ladder, the other of the side bars l4 of each of the trestle ladders is formed with a sharper beveled surface 40 so that a wedge member 42 will fit between and en.- gage the beveled surface 40 and a face of the side bar 32 of the extension ladder, as clearly shown in Fig. 1. As will be hereinafter described, the weight of the extension ladder and the load thereon tends to force the wedge 42 downwardly and therefore firmly grips the extension ladder and prevents side sway and wabbling.

The ladder look as illustrated in Figs. 3, 4 and includes a housing 44 attached to a side bar M of the trestle ladder by the plate 46 which is securely held by the nut and bolt members l8. It should be understood that two of the ladder locks are used, one being attached to each of the trestle ladders on opposite relative sides. The wedge member 42 is connected by pivot pin 48 to a link member 50 which has depending arms 52 spaced apart to receive the upper end of the housing 44. Pin 54 extends through the lower ends of the arms 52 and is received in vertical slots 56 formed in the sides of the housing at the upper end thereof. Within the housing a hook member 58 is mounted on the pin 54 and is normally swung so that the hook portion 60 protrudes outwardly from the housing by the provision of spring 62 which is connected at one end 64 to the hook member and at its other end 66 to the housing. It will be apparent that the spring 62 acts to swing the hook member from the position shown in Fig. 5 towards the position illustrated in Fig. 3. The'lower portion of the hook member is formed with a depending tongue 68, the outer face of which is formed to be engaged by the rungs 34 of the extension ladder, as will be later described. The housing 34 also constitutes a mounting for a trigger finger 1B which is pivoted at 12 in the housing and which is formed with cam portions 14 adapted to engage the hook member 58 to normally hold the trigger Ill in a raised or lowered position, but without looking the trigger memberso as to prevent movement from such positions.

The operation of the trestle ladder will be readily apparent from Figs. 3 and 5. In order to raise the extension ladder to the desired height it is 2 only necessary to grasp the lower end and push upwards, the upward movement on the ladder is illustrated in full lines in Fig. 5 and in dotted lines in Fig. 3. Each rung will engage the tongue 68 of the hook member thereby forcing the hook member into the housing and passing over the tip of the hook portion 60 as shown in Fig. 5. Also each rung will readily pass the trigger finger as indicated in Fig. 3. When the extension ladder has been raised to its desired position and one of the rungs of the extension ladder is between the trigger finger and hook member as indicated by the dotted lines in Fig. 3, the extension ladder is lowered for a short distance, whereupon the rung will engage in the hook portion of the hook member and the weight of the extension ladder will thereby be transmitted to the hook member. The load will be transmitted from the hook member to the link 52 and thus to the wedge member 42 so that the extension ladder will not only be automatically looked in position, but the locking action will also serve to wedge the extension ladder in position.

When it is desired to lower the extension ladder it is only necessary to raise the extension ladder until the rung which has been locked has passed over the trigger finger 10, then the ladder can be lowered, bringing the trigger finger to the position illustrated by the dotted lines in Fig. 5, in which position the trigger finger will act to force the hook member inwardly and permit lowering of the extension ladder. Thus the ladder extension part of the trestle ladder may readily be adjusted by a workman from the ground, and it is unnecessary to climb the ladder to lock the parts in position.

In operation of the ladder lock and wedge it should be understood that the tension spring 62 performs a double function. The spring is arranged at such an angle that it not only urges the hook shaped member to swing about the pivot 54 but also tends to cause upward movement of the member 58 to move the pivot 54 bracket 52 and to release the wedge 42.

I claim:

1. In an extension trestle ladder a pair of trestle ladder members hinged at their upper ends and adapted to be outwardly spread apart at their lower ends to rest upon the ground, an extension ladder member vertically slidable between said trestle ladder members, and automatic locking means for the extension ladder comprising a lock housing, a bracket for the lock housing and fixed to a trestle ladder member for holding said lock housing in a vertical position, a hook shaped looking member movably mounted in said housing and resiliently urged to swing outwardly therefrom into engagement with a rung of the extension ladder and a movable trigger mounted in said housing above said locking member and cooperating therewith to permit downward movement of the rungs of the extension ladder past said locking member.

2. In an extension trestle ladder a pair of trestle ladder members hinged at their upper ends and adapted to be outwardly spread apart at their lower ends to rest upon the ground, an extension ladder member vertically slidable between said trestle ladder members, and means operable by movement of said extension ladder for wedging said extension ladder in fixed position comprising a hook shaped member adapted to be engaged by a rung of the extension ladder, a wedge member connected to said hook shaped member for movement therewith, said wedge member being adapted to engage between adjacent faces of said extension ladder and one of said trestle ladders.

3. In an extension trestle ladder a pair of trestle ladder members hinged at their upper ends and adapted to be outwardly spread apart at their lower ends to rest .upon the ground, an extension ladder member vertically slidable between said trestle ladder members, and means operable by movement of said extension ladder for automatically locking and wedging said extension ladder in fixed position comprising a housing fixed to one of said trestle ladder mem-- bers, a hook shaped locking member mounted in said housing for limited vertical movement with respect to said housing and to swing outwardly or inwardly with respect to said housing, resilient means normally urging said hook shaped member outwardly from said housing into engagement with a rung of the extension ladder, a trigger pivotally mounted in said housing and adapted to engage said hook shaped member in one position to permit downward movement of the rungs of the extension ladder past said hook shaped member, a wedge member positioned outwardly of said housing between adjacent faces of said extension ladder and one of said trestle ladders and means connecting said wedge member to said hook shaped member whereby the load of the extension ladder is transmitted to said wedge through said locking member when said extension ladder is in locked position.

4. In an extension trestle ladder a pair of trestle ladder members hinged at their upper ends and adapted to be outwardly spread apart at their lower ends to rest upon the ground, an extension ladder member vertically slidable between said trestle ladder members, and automatic locking and wedging means mounted on both of said trestle members and including a pair of hook shaped locking members adapted to engage a rung of the extension ladder from each side thereof and a pair of wedging members connected to said locking members positioned between the side bars of said extension ladder and the upper ends of said trestle ladders whereby the load upon the extension ladder is transmitted through said hook shaped members to said wedge members to hold said extension ladder firmly in position with respect to said trestle ladders.

5. An automatic lock and wedge for an extension trestle ladder comprising a housing adapted to be fixed to a trestle ladder, said housing having slots in the side walls thereof, a pin extending through said slots for vertical movement with respect to said housing, a hook shaped member pivotally mounted in said housing on said pin and adapted to engage a rung of the extension ladder, a tension spring connected to said housing and said member to urge said member to swing outwardly, a bifurcated member fitting over the upper end of the housing and connected to said pin, and a wedge member pivotally mounted on said bifurcated member laterally thereof and adapted to engage adjacent faces of a trestle ladder and the extension ladder.

6. A ladder lock and wedge for an extension ladder comprising a lock housing adapted to be fixed to the stationary part of the extension ladder, a rung engaging locking member mounted in said housing for vertical and swingable movement with respect thereto, a tension spring urging said member to swing outwardly and to move upwardly with respect to said housing, and a wedge member connected to and actuated by the vertical movement of said locking member and adapted to engage adjacent faces of the relatively movable ladder members.

CHARLES A. BARRETT. 

